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The quasar has a large-scale visible jet, which measures ~200 kly (60 kpc) long, having an apparent size of 23″.[4] In 1995 optical imaging of the jet using the Hubble Space Telescope revealed a structured morphology evidenced by repeated bright knots interlaced by areas of weak emission.[4]

Prior to the discovery of 3C 273, several other radio sources had been associated with optical counterparts, the first being 3C 48. Also, many active galaxies had been misidentified as variable stars, including the famous BL Lac, W Com, and AU CVn. However, it wasn't understood what these objects were, since their spectra were unlike those of any known stars. Its spectrum did not resemble that of any normal stars with typical stellar elements. 3C 273 was the first object to be identified as what we now know quasars to be—extremely luminous objects at cosmological distances.

3C 273 is a radio-loud quasar, and was also one of the first extragalactic X-ray sources discovered in 1970.
However, even to this day, the process which gives rise to the X-ray emissions is controversial.[4]
The luminosity is variable at nearly every wavelength from radio waves to Gamma rays on timescales of a few days to decades.
Polarization with coincident orientation has been observed in radio, infrared, and optical light being emitted from the large-scale jet; these emissions are therefore almost certainly synchrotron in nature,[4] radiation that is created by a jet of charged particles moving at relativistic speeds.
Such jets are believed to be created by the interaction of the central black hole and the accretion disk. VLBI radio observations of 3C 273 have revealed proper motion of some of the radio emitting regions, further suggesting the presence of relativistic jets of material. [10][11]